The present invention relates basically to the field of carburetion for internal combustion engines and more particularly to carburetors utilizing a variable venturi in place of the conventional butterfly type arrangement and fixed venturi.
Most present automobile carburetors are designed with a fixed venturi to create a designated vacuum pressure within the induction duct in order to pull hydrocarbon fuel from a fuel reservoir. The fuel reservoir is usually an integral portion of the carburetor and is supplied with raw fuel from the fuel supply tank through a volumetric control arrangement utilizing a float and associated valve mechanism. In sophisticated carburetors, more than one chamber is provided with additional float assemblies, primarily for the reason that the fuel level fluctuates drastically as the associated automobile changes position while cornering or going up or downhill. By situating the float chambers on opposite sides of the carburetor, this problem is alleviated to some extent. Obviously the design consideration involved is that the more chambers utilized, the better the control of the fuel level within the multiple chambers during various physical changes occurring during climbing, descending, cornering, acceleration, deceleration, and other situations wherein fuel level fluctuations may be expected.
An additional problem remains with the conventional float system regardless of the number of individual floats and reservoir chambers provided. This problem is that the selected fuel level is maintained continuously only when the engine is operating at a steady RPM level. When demand is suddenly placed on the reservoir for additional fuel (occurring when the operator suddenly depresses the accelerator to the floor) the fuel level will correspondingly drop as the fuel is used. This lowers the float which finally opens the float valve wider. It is precisely at this phase of operation when the fuel level should be at its highest point and maintained at that point in order to answer to the demands of the full throttle condition. Otherwise the engine will struggle for a period of time until the float valve opens a sufficient amount and the fuel pump is allowed to operate to deliver the demanded fuel directly to the fuel discharge orifice of the carburetor. Thus, it may be easily understood that it would be very desirable to obtain some form of carburetion system whereby a continuous volume of fuel is maintained at all times regardless of engine operating conditions in order that an immediate fuel supply is available in response to any demand placed on the fuel delivery system by sudden changes in the throttle setting.
The fixed venturi form of carburetor, by its nature, operates at a maximum efficiency only over a relatively small range of engine RPM. Furthermore, a different size venturi is generally required for different performance requirements. Automobiles are seldom operated in the restricted range of RPM in which the fixed venturi operates at maximum efficiency. Consequently, various complicated venturi arrangements including multiple venturi tubes have been included in carburetors in attempts to make the carburetor more efficient over a wider range of operating conditions. Often, an accelerator pump is provided in addition to multiple venturi tubes to operate in response to sudden depression of the throttle pedal. Such accelerator pumps usually function to pump large amounts of raw fuel directly into the air moving through the venturi. Accelerator pumps are responsible for a tremendous loss of usable fuel that is simply carried through the engine and entered into the air as unburned hydrocarbons. They therefore result in poor fuel economy and generally increase the pollution output of a possibly cleaner burning engine.
It may be seen then that additional features added to existing fixed venturi carburetors frequently are the source of additional inefficiencies that often do more harm than the good they were intended for. Nearly all the additional features on the contemporary complex carburetors are designed to compensate for the inefficiency of the venturi over the full range of operating conditions and RPM. Ideally, a carburetor should operate at maximum efficiency over the full range of engine operating RPM and load conditions.
Conventional air valve type carburetors have been utilized in an attempt to maintain a constant air velocity across a fuel jet orifice independent of the throttle valve position and engine speed. Such carburetors are designed in an attempt to vary the size of the fuel jet in accordance with the amount of air entering the carburetor to therefore provide a correct "air-fuel rato." Engines having such air valve carburetors are generally difficult to start and to operate at idling RPM.
One of the primary objects of this invention is to provide a variable venturi carburetor that is capable of effectively premixing the fuel and air over the full range of engine operation prior to emittance of the fuel into the main air duct of the carburetor.
Another object of this invention is to provide a variable venturi carburetor that is capable of automatically adjusting the fuel and air in response to the engine demand while continually premixing the fuel and air prior to induction into the throat of the variable venturi.
A further object is to provide a variable venturi carburetor that utilizes an annular fuel orifice circumscribing the main induction duct and utilizing heat and vacuum pressure to effectively premix the fuel vapors and air prior to passing the premixture through the annular orifice into the main induction duct.
One object of the present invention is to provide a variable venturi carburetor that includes a float system wherein a fuel level may be maintained regardless of the running condition of the associated engine to thereby provide a ready supply of fuel regardless of demand from the engine.
Another object is to provide such a carburetor wherein there is included a fuel reservoir that is not adversely affected by acceleration forces exerted on the carburetor which occur when the vehicle accelerates, decelerates and turns a corner.
A still further important object is to provide such a carburetor that includes a fuel mixture control means by which the fuel-air ratio is changed in response to differing throttle positions. Thus, at a full throttle or in an extreme accelerating condition, a rich supply of fuel is delivered to the primary airstream passing through the carburetor, while at idle speeds, the ratio is allowed to change through functioning of the mixture control means and specially provided idle air and fuel systems to produce the proper ratio of fuel to air during idle conditions.
A further object is to provide such a carburetor that relies only upon axial movement of a central venturi member to control different throttle settings of the carburetor and is not dependent upon a conventional form of butterfly throttle valve.
A yet further object of my invention is to provide such a carburetor that may be utilized as either an updraft or a downdraft form of carburetor.
A still further object is to provide such a carburetor that, in a modified form may provide even greater area of discharge for premixed air and fuel by providing two oppositely facing fuel discharge orifices.
An additional object is to provide such a carburetor that is extremely simple in construction in relation to conventional carburetors, and that is therefore relatively easy to maintain and adjust, and is also easy to manufacture and inexpensive to purchase.
An additional object is to provide such a carburetor that is easily adapted to be mounted on a great variety of internal combustion engines without requiring substantial modification thereof.
These and still further objects and advantages will become evident upon reading the following detailed description which, taken with the accompanying drawings, discloses a preferred form of my invention. However, it is to be understood that the following description is given merely by way of explanation of a preferred and alternate form of my invention and that various changes and modifications may be made therein without departing from the intended scope of my invention. Thus, only the claims to be found at the end of this specification are to be taken as definitions of my invention.